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Dust Mite Allergy Avoidance

The Asthma Center, Allergic Disease Associates, P.C.
Professional Arts Building
205 North Broad Street, Ste 300
Philadelphia, PA 19107


House dust contains a variety of materials including fabric fiber, human skin scales, animal dander, bacteria, insect parts, mold spores, food particles, as well as other synthetic and organic material and dust mite. Of all the components of house dust, the house dust mite is the most important, causing the most problem to allergy sufferers. These creatures are not true insects but are arachnids closely related to spiders, chiggers, and ticks. Dust mites cannot be seen without the aid of a microscope. They feed off of skin scales and dander shed by humans and indoor animals. Studies in the United States have shown that 30-40% of all asthmatics and the majority of patients with hayfever are allergic to dust mite. Atopic dermatitis is also commonly triggered by mite sensitivity.

Because human skin scales are the major food source for dust mites, they tend to live in bedding, carpeting, curtains, upholstered furniture, heating, and air-conditioning ducts, clothing, closets, and car seats. They thrive when the temperature is warm (70-90 degrees) and when the relative humidity is 75-80%. Dust mites cannot survive when the relative humidity falls below 40% or at very high altitudes (greater than 9,000 feet elevation) or when it is too cold. They can, however, survive vacuum cleaning because they are able to burrow deep into carpets. Mites do not bite, do not live on human skin, nor do they transmit disease. The only human illness dust mites cause is allergy.

Approximately 100 to 400 dust mites have been counted in one gram of house dust (approximate weight of a paperclip) and populations in the millions can be found in mattresses, pillows, and box springs. Mite populations peak in home environments in July and August and remain high through December. Mites and mite particles can be found anywhere dust accumulates, although they are not common components of surface dust. Mite allergens are carried on relatively large particles that remain in the air only a few minutes after being disturbed. Therefore, the vast majority of dust mites are not in the air. People become allergic to proteins in mite body parts and mite feces. These fecal pellets are as tiny as some pollen grains and can float easily into the air and get carried into the nose and lungs. Mites become airborne when dust is stirred up by vacuum cleaning, during pillow beating, and with curtain shaking. Forced-air heating systems can also exacerbate dust mite allergy by sending these allergens into the air. When sensitive individuals come into contact with mite allergens, hayfever, asthma, and/or skin eczema can result.

Since dust mites cannot be seen by the naked eye, most people are usually unaware of the connection between dust mite allergy and their symptoms. Mite allergy can best be diagnosed by allergy skin testing. This is the easiest, most sensitive, and least expensive way of making the diagnosis. Avoidance, medications, and allergy injections (immunotherapy) are the main treatment modalities for dust mite allergy.

The following measures can help reduce dust mite levels in the home environment and have been shown in clinical studies to successfully reduce dust mite populations and improve symptoms.

  1. Reduce dust content of the home, especially in the bedroom (review house dust control instructions and air cleaner information).
  2. Eliminate carpets and upholstered furniture where possible since they are breeding grounds for mites. This is particularly important where carpeting is laid over concrete, like in basement areas. If carpeting is essential, low pile synthetic carpets and washable scatter rugs are preferred. Optimal flooring is wood, seamless linoleum or vinyl flooring.HEPA-containing vacuum cleaners like the Nilfisk and Miele (canister types) or Fantom (upright type) machines or placing special microfilter bags on standard upright vacuum cleaners are superior to conventional vacuums (we do not recommend Rainbow, FilterQueen, Kirby, or Electrolux machines). Vacuuming of carpets and upholstery 2 times per week is important as well as wearing a dust mask for sensitive individuals while vacuuming. Bedrooms in particular, should be aired out after vacuuming except during significant pollen seasons. Since tight energy efficient homes have less fresh air, such homes tend to have higher indoor mite levels.
  3. Keep humidity at 50% or lower to retard mite growth (using a hygrometer may be helpful to measure indoor humidity). Run a dehumidifier or air conditioner when humidity is high, particularly from spring through fall. Be careful when using bedroom humidifiers and cool mist vaporizers since excessive moisture will increase mite and mold levels in the bedroom.
  4. Replacing used bedding material - mattress, box spring, pillow, blankets - is one of the most highly effective measures in reducing dust mite allergen exposure. In addition, new or used bedding material should be enclosed separately in hypoallergenic plastic or vinyl impenetrable encasings to reduce mite populations and limit exposure during sleep. Place tape over the zipper of these encasings and cover the mattress encasings with a washable mattress pad. These products vary in quality and one should choose products based on both comfort and their durability. These covers should be wiped at least once a week as well.Waterbeds are not a "hypoallergenic" alternative to box springs or mattresses since mite levels are just as high on waterbeds as regular bedding material. Electric blankets may be helpful in killing off dust mites. However, the small but real risk of starting a fire outweighs the benefits of electric blankets.
  5. Stuffed animals should be minimized in the bedroom environment and washable products are preferable. GUND brand stuffed animals are washable. Minimize other fabrics in the bedroom like upholstered furniture and fabric curtains.
  6. Avoid feather pillows, down comforters, and woolen blankets since they may harbor dust mites. Washable blankets and quilts of synthetic materials are preferable. Use Dacron or other synthetic polyester pillows and replace yearly and regularly wash them in hot water, especially if plastic encasings are found uncomfortable.
  7. Wash all bedding linens and blankets in hot (greater than 130 degrees) water every 7 - 10 days which will kill dust mites. Hot drying is not as lethal as hot water washing, and cold water washing allows 10% of mites to survive. Dry cleaning blankets can also reduce mite contact.Personal clothing may also be an important source of dust mite exposure. Regular washing, preferably in hot water or dry cleaning may remove and/or kill dust mites in clothing. In addition, clothing should be stored under dry conditions or be laundered/dry cleaned after prolonged storage.
  8. Shower and shampoo before bedtime to wash off shedded skin and dandruff that could otherwise serve as a food source for mites in bedding material.

Several commercially available preparations are available to kill or break down or degrade dust mites. The general term for these products is acaricides. It should be kept in mind, however, that dead dust mite parts can stay in carpeting and bedding materials for several months and can continue to cause allergy long after the mites have died. Therefore, acaricides should be used as adjuvants to the other environmental control measures discussed above.

Paragerm is a nontoxic acaricide that has been used extensively in Europe and acts promptly and is easy to use.A two minute spray is usually effective and lasts for about 2 months. Unfortunately, it has an offensive odor.

Tannic Acid breaks down protein and a 4 hour treatment of carpet with tannic acid significantly reduces dust mite allergen levels. Tannic acid, however, does not kill dust mites. The ability of tannic acid to denature proteins also makes it effective in reducing animal allergen levels, particularly cat allergens. High levels of cat allergen, however, will block the effective use of tannic acid on dust mite protein. Tannic acid is not recommended for white carpets since discoloration may occur. Because it does not kill dust mites, the application must be repeated every 6 to 8 weeks.

Sunlight - Studies from Australia have shown that a 3 hour exposure of mite infested carpet to sunlight results in complete killing of all dust mites. This technique, however, has limited application in the U.S. except in selected warm areas.

Benzyl benzoate powder (Acarason) is a repellent acaricide that is commercially available as a moist powder. It has a long safety record in humans since it is also used as a preservative for foods. The powder should be applied at night, brushed into the carpet, left overnight for 12 hours, and brushed into the carpet again before vacuuming. Its effect may last from 6 weeks to 3 months. This is not effective on wood floors. Unfortunately, it is not always as potent after storage, and it is recommended that an opened bag be used immediately and then discarded. Pets and infants should be kept off the treated carpet until it has been vacuumed, and contamination of food and water should be avoided.

All commercially available acaricides are somewhat expensive and treatment must be repeated several times per year and may be unpleasant to use because of odor or discoloration of carpets. They do, however, offer an effective adjuvant to dust mite allergy control for the patient who refuses to part with carpeting.

Medications may also be prescribed to help your symptoms. If these measures are unsuccessful, allergy injections may be recommended since they are very effective for dust mite allergy.

For more information on HEPA-containing vacuum cleaners, microfilter bags for upright vacuums, humidistats, hygrometers, dust masks, encasings and acaricides, the following mail order companies are recommended: